Searching for Trojan Asteroids

Even as NASA’s Kepler Space Telescope continues to chart new planets around distant stars at an impressive rate, data gathered from another NASA spacecraft, the Wide-field Infrared Observatory (WISE), is shedding light on a particular class of asteroids shadowing planetary orbits in our home system.  Labelled as Trojan asteroids following the initial discovery of  the asteroid “Achilles” in a position ahead of Jupiter in 1906, they can precede or follow a planet’s orbit. In the most recently released analysis,  the Jovian Trojans appear to be distinctly different from both Kuiper and main belt asteroids, and may represent a  sample of the earliest building blocks of the solar system, frozen in time.

The gradually developing knowledge base on Trojan asteroids, which have also been discovered in the orbits of Mars and Neptune,  is suggesting that they may be far more common than once thought. Earth has one confirmed Trojan, 2010 TK7 which was discovered by WISE in 2011.    Although it is the only such Earth Trojan to be discovered to date, there mmay in fact be many more.  The search for Earth Trojans from ground based telescopes is limited by the fact that the relative positions in Earth’s orbital path are in sunlight, obscuring observation.

The most intriguing thing about the potential of additional Trojans is the relative ease with which they could be reached from Earth due to the small amount of Delta-V required to make the trip.  While 2010 TK7 is not a good candidate because it is in a corkscrew pattern which carries it far afield, other Earth Trojans might be considerably more accessible, offering the potential of comparatively low cost robotic missions to characterize their suitability for human visitation, and possible resource utilization.

The WISE mission was terminated in 2011 following the loss of hydrogen cooling,  with the spacecraft remaining in a polar orbit.